As a method of forming/displaying a stereoscopic image without using any spectacles, a lenticular method that displays a stereoscopic image using a lenticular lens sheet, and a parallax barrier method that displays a stereoscopic image using a slit called a parallax barrier are widely known, and an object to be displayed on which a stereoscopic image is formed, its display apparatus, and the like using these methods are known.
The lenticular method had been extensively studied since 1970, and its effects are described in, e.g., Oplus E, November 1993, pp. 100–104.
The parallax barrier method is disclosed in, e.g., S. H. Kaplan “Theory of Parallax Barriers”, J. SMPTE Vol. 59, No. 7, pp. 11–21 (1952).
The presence of the right and left eyes of a human being is important for the display of a stereoscopic image, and it is a common practice to specify the generating line direction (lens forming state) of the lenticular lens so as to recognize parallax or disparity images in the vertical direction (since parallax images are hardly recognized stereoscopically in the horizontal direction).
Since a moving image can be obtained in the same manner, this process will be briefly explained below.
Conventionally, moving image display panels that apply a lenticular lens are used in toys or for promotion purposes. Such panel displays a plurality of images on a single surface, and the observer can see a first or second image depending on the direction in which he or she observes the panel. This display panel has a structure in which original images are formed by a special method on the reverse surface of a planar lens (lenticular lens), on the obverse surface of which a large number of cylindrical lenses (quadric lenses having a hog-backed (semi-cylindrical) section). Stripe images obtained by cutting the first and second images into stripes are alternately arranged at the pitch of the lenticular lens, i.e., within the width of each individual cylindrical lens, and the observer can observe as if the first image has moved (changed) to the second image, since either the first or second image enters the eyes depending on the angle that the observer observes the lenticular lens. These images may use characters which are not successive in terms of shape, or may use successive moving images like a golf swing. Also, the number of images is not limited to two, and three or more different images (a maximum of eight different images) may be mixed to express images in turn.
The presence of the right and left eyes of a human being interferes with the display of a moving image, and it is a common practice to specify the generating line direction (lens forming state) of the lenticular lens so as to recognize images in the horizontal direction (since images are mixed in the vertical direction, and a change in image becomes vague.
Furthermore, the stereoscopic image forming apparatus has various means to easily generate an image.
For example, as a simple image forming method, Japanese Patent Laid-Open No. 10-293266 has proposed an image generation apparatus. As for pitch alignment between the lenticular lens and images, Japanese Patent Laid-Open No. 6-340099 has proposed a method using an optical sensor, and Japanese Patent Laid-Open No. 9-15766 has proposed a method of controlling ink-jet ejection timings. Furthermore, Japanese Patent Laid-Open No. 6-209400 has proposed a method of directly printing images on the reverse surface of a sheet-like lenticular lens, and Japanese Patent Laid-Open No. 9-102968 has made a proposal pertaining to the relationship with a binary printer.
Also, many display apparatuses for decorating these stereoscopic images have been proposed.
As an example of such display apparatuses, Japanese Patent Laid-Open Nos. 8-320659 and 8-320660 have proposed an arrangement which aligns a plurality of patterns to a storage case having a lenticular lens to increase contact between them. Also, Japanese Patent Laid-Open No. 11-259614 has proposed a card case and card. Furthermore, many applications to CD cases, cassette cases, and the like have been proposed. For example, Japanese Patent Laid-Open Nos. 9-30581, 9-309583, and the like are known.
However, in the method of aligning a lenticular lens to a plurality of patterns, as described in Japanese Patent Laid-Open Nos. 8-320659 and 8-320660, only an arrangement for aligning to a plurality of positions with reference to one position as an adjustment margin is described. However, it is difficult to attain tilt correction or delicate alignment with reference to only one position. Also, as for contact, only an arrangement for increasing contact by linearly pressing a plurality of portions by pressing members using spring members such as elastic members or the like from the reverse surface is disclosed. But this arrangement is not suitable bringing the entire surface of a thin, flat object having no stiffness such as a paper sheet into tight contact with the case by uniformly applying a pressure to it. Furthermore, in the conventional display apparatus represented by Japanese Patent Laid-Open No. 11-259614, only an outline of an arrangement is described, and no descriptions about a method of displaying a recent high-resolution stereoscopic image (a plurality of layers of stereoscopic images) and moving image (two or three or more layers of moving images), and their alignment are available. When the lens and case are independently movable, if alignment is insufficient especially in case of moving images, crosstalk of images (the observer sees a portion of an image that he or she does not want to observe, and feels distracted) occurs. In order to display a high-resolution stereoscopic image and moving image with high image quality, the contact between the lenticular lens and printed images (objects to be displayed) is important. If an image locally lifts, the image becomes unsharp, the stereoscopic effect impairs, and so forth. As a result of our examination, it is very difficult to display an especially high-resolution stereoscopic image/moving image (images output by a printing apparatus having an output resolution of 400 dpi or higher and, preferably, 600 dpi or higher) with high image quality. On the other hand, there is no description about compatibility with recent photo printers represented by ink-jet printers. Furthermore, as for the print size, only a case of a card or at most a cassette case is described, while the aforementioned tendency is protected to grow as the size of an output object becomes larger (postcard size or larger). Moreover, a lenticular lens which is compatible to the high-resolution output has a very small lens pitch, and end users cannot discriminate the obverse and reverse surfaces of the lens. If the user uses the wrong surface, the effect of a stereoscopic image/moving image cannot be obtained, and a method of easily discriminating the obverse and reverse surfaces of the lens is demanded.